Sensor probes may be used to measure a concentration of an analyte in a liquid media surrounding living cells as a means to interrogate the behavior of the cells and, in particular, to profile behavioral changes that are induced by exposure of the cells to candidate drug compounds. An example of an apparatus and method for making measurements of this type is described in U.S. Patent Publication No. 2005/0054028, the disclosure of which is incorporated by reference herein in its entirety.
One problem that may be encountered in using such a method is that an equilibration period may be required each time that the submersible sensor probe is placed in or otherwise exposed to the cell media. The equilibration period may be preferable or required to allow time for the probe to adjust to the temperature of the media, or for the sensor or its associated electronics to adapt to the difference between ambient air and the cell media. Such equilibration may require seconds, minutes, or hours depending, for example, on the sensor and measurement sensitivity desired.
The equilibration process may be undesirable to the user of the apparatus, because it may lengthen the time needed for analysis, and potentially may result in a measurement error if sequential equilibrations have differing characteristics.
A typical reason for removing a sensor probe from the cell media is to allow the addition of a test compound such as a drug candidate. This is particularly likely when the sensor probe is part of an assembly containing an array of probes, and when the test compound is delivered using an array of delivery devices such as pipettes, e.g., controlled and implemented by a robot.